The present invention relates to the general field of making case turbine casings out of composite material, and it relates more particularly to gas turbine fan retention casings for aeroengines.
In a gas turbine aeroengine, a fan casing performs several functions: it defines the passage for admitting air into the engine, it supports an abradable material in register with the tips of the fan blades, it supports an optional structure for absorbing soundwaves to perform acoustic treatment at the inlet to the engine, and it incorporates or supports a retention shield. The shield constitutes a trap for retaining debris that has been projected by centrifuging, e.g. such as items that have been ingested or fragments of damaged blades, for the purpose of preventing them from passing through the casing and reaching other parts of the aircraft.
It is common practice for a fan retention casing to be made up firstly of a relatively thin wall defining the air inlet passage and supporting an abradable material in register with the path followed by the tips of the fan blades, and also supporting the acoustic treatment coating, if any, and secondly of a shield structure that is fastened to said wall on the outside, around the fan.
Proposals have already been made for making a fan retention casing out of composite material. By way of example, reference may be made to Document EP 1 961 923, which describes fabricating a casing out of composite material of varying thickness, by forming fiber reinforcement out of superposed layers of a fiber texture and densifying the fiber reinforcement with a matrix. More precisely, that document makes provision for using a take-up mandrel during the three-dimensional weaving of the fiber texture, with the texture then being wound in superposed layers on an impregnation mandrel that present an outer surface of profile that corresponds to the profile of the central portion of the casing to be fabricated together with two cheekplates corresponding to fastener flanges of the casing. The fiber preform as obtained in this way is held on the impregnation mandrel and is impregnated with resin prior to polymerizing the resin.
A practical implementation of that method raises the problem of transferring the fiber texture from the take-up mandrel to the impregnation mandrel. To solve that problem, the Applicant has made proposals in French patent application FR 11/53212 (not yet published) for a winding machine that makes it possible while transferring the fiber texture from the take-up mandrel to the impregnation mandrel both to place the fiber texture correctly on the impregnation mandrel and to apply an appropriate winding tension.
With such a machine, there arises the problem of holding the fiber texture on the impregnation mandrel when starting winding. Since winding is performed directly onto the mandrel that is to be used when impregnating it with the resin, the mandrel is smooth and therefore does not present any attachment means on its surface. This problem of holding the fiber texture on the impregnation mandrel also arises at the end of winding where, prior to cutting the fiber preform to its final length, it is necessary to hold the fiber preform while not losing the tension that was applied to the texture while it was being wound.
Consequently, there exists a need for tooling that makes it possible to hold the fiber texture on the impregnation mandrel at the beginning of winding and at the end of winding.